1] The Institute of Optics, University of Rochester, Rochester, New York 14627, USA [2] Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, A-1090 Vienna, Austria.
The Institute of Optics, University of Rochester, Rochester, New York 14627, USA.
Nat Commun. 2014;5:3115. doi: 10.1038/ncomms4115.
The measurement of a quantum state poses a unique challenge for experimentalists. Recently, the technique of 'direct measurement' was proposed for characterizing a quantum state in situ through sequential weak and strong measurements. While this method has been used for measuring polarization states, its real potential lies in the measurement of states with a large dimensionality. Here we show the practical direct measurement of a high-dimensional state vector in the discrete basis of orbital angular momentum. Through weak measurements of orbital angular momentum and strong measurements of angular position, we measure the complex probability amplitudes of a pure state with a dimensionality, d=27. Further, we use our method to directly observe the relationship between rotations of a state vector and the relative phase between its orbital-angular-momentum components. Our technique has important applications in high-dimensional classical and quantum information systems and can be extended to characterize other types of large quantum states.
量子态的测量对实验物理学家来说提出了独特的挑战。最近，“直接测量”技术被提出，通过顺序的弱测量和强测量来对量子态进行原位表征。虽然这种方法已经被用于测量极化态，但它的真正潜力在于对具有大维度的态的测量。在这里，我们展示了在轨道角动量离散基下对高维态矢量的实际直接测量。通过对轨道角动量的弱测量和对角度位置的强测量，我们测量了具有维度 d=27 的纯态的复概率幅度。此外，我们使用我们的方法直接观察了态矢量的旋转与轨道角动量分量之间的相对相位之间的关系。我们的技术在高维经典和量子信息系统中有重要的应用，并可以扩展到对其他类型的大量子态的表征。
